But once I then synchronise my user files through OneDrive, that change would be transferred to my other computer. So I will only use that if I am doing something on the notebook that requires correct multi-media links.
Yes they are marked Primary, but Renee has identified the problem, thanks.
Sometime in the past I must have changed the directory structure where many of my photos are stored. I have now produced the chart I wanted.
My data is in D: drive on the desktop, but the O/S of my notebook has allocated D: for the recovery drive, so data is in F:, hence none of my photos link correctly when I open RM in the notebook. I have to re-install the O/S anyway, so I had better fix that at the same time.